In marine seismic exploration, a cable, commonly referred to as a seismic streamer cable, is towed underwater by a surface vessel. Conventional marine seismic surveys generally involve towing one or more streamer cables with a seismic vessel, where each streamer comprises a plurality of receivers distributed along its length. Depending on example, suitable seismic receivers or seismic node devices can be deployed along a number of individual cables or node lines, which are spread out into an array behind the tow vessel.
In addition to towed seismic survey applications, seismic receivers and nodes can also be deployed in an array of ocean bottom cables, suspended at a particular depth above the seafloor (or below the ocean surface), or deployed as an array of autonomous seismic sensor stations. Suitable seismic systems for use in such applications include, but are not limited to, those described in U.S. Publication No. 2015/0098302 to Olivier et al. (application Ser. No. 14/498,341), entitled SEISMIC SENSOR, and U.S. Publication No. 2015/0331126 to Lambert et al. (application Ser. No. 14/710,373), entitled OCEAN BOTTOM SYSTEM, each of which is incorporated by reference herein, in the entirety and for all purposes. Other suitable seismic systems are described in U.S. Pat. No. 8,730,766 to Lambert et al., entitled SEISMIC SYSTEM WITH GHOST AND MOTION REJECTION, U.S. Pat. No. 9,081,120 to Olivier, entitled APPARATUS AND METHOD FOR LOW-TENSION RETRIEVAL OF INSTRUMENTED MARINE CABLES, and U.S. Publication No. 2016/0033660 to Olivier et al. (application Ser. No. 14/774,544), entitled INTERNAL BEND RESTRICTOR FOR OPTO/ELECTRICAL ARMORED CABLES, each of which is also incorporated by reference herein, in the entirety and for all purposes.
Each seismic receiver or node may include, for example, a pressure sensor and/or a particle motion sensor in proximity to one another. The pressure sensor may be configured, for example, as a hydrophone that records scalar pressure measurements of a seismic wavefield in the surrounding water column or other seismic medium. The motion sensor may be configured, for example, as an accelerometer configured to sense linear or rotational motion (or both), e.g., with respect to one or more independent axes. In addition, positioning and navigation equipment may also be incorporated within or attached externally to the streamer cables or nodes, providing active means of controlling depth and lateral offset.
In operation of such a system in a seismic survey, an acoustic source is fired which generates an impulse of compressed air, creating an air bubble in the water column. The collapse of the bubble generates acoustic pulses that radiate through the water, propagating through the surrounding seismic medium and penetrating and into the earth below. By analyzing the reflected seismic wavefield detected by the receiver(s) or node(s) during the survey, geophysical data pertaining to reflected signals can be acquired and these signals may be used to form an image indicating the composition and subsurface structure of the Earth near the survey location.
In order to generate a high resolution images of the subsurface structure, with reduced distortion or substantially free of distortion, the seismic system may incorporate or provide one or more of (1) precise knowledge of source to receiver timing, (2) precise source to receiver geometry, and (3) broadband acoustic sensors having high signal to noise performance. To address these three survey considerations, the network of receivers may be positioned on a common plane, and deviations from the plane may have an impact on image quality—sometimes, the effect on image quality may be disadvantageous or deleterious. Thus, there remains a need for improved trim control and positioning capabilities that overcome the limitations of existing technologies, including, but not limited to, the known programmability limitations of current streamer recovery device (SRD) systems and related product offerings.